From ACME v2 API Staging Availability (Jan 2):
And from ACME v2 API Endpoint Coming January 2018 - Let's Encrypt :
We are not setting an end-of-life date for the ACME v1 protocol because we don’t yet have enough data to determine when would be an appropriate date. Once we’re confident that we can predict an appropriate end-of-life date for our ACME v1 API endpoint we’ll announce one.
As far as I know they didn't made another announcement since.